Droplets have memory, too: A study of transient heating on droplet evaporation

Under transient heating, droplets can evaporate very differently than those that experience consistent heating. This can be observed in aerospace technology, where droplets can be exposed to intense thermal changes in a matter of seconds.

Sigalotti et al. used high-fidelity 3D smoothed particle hydrodynamics simulations to understand the evaporation of droplets suspended in zero gravity that are exposed to transient heating. By using simulations instead of high-speed cameras, they could observe the transitions between the liquid-vapor interfaces with more precision.

“Every particle can be precisely tracked through simulations, offering a level of detail about interfacial dynamics and internal energy fluxes that is not possible with current experimental hardware,” author Leonardo Sigalotti said.

Under consistent heating conditions, droplets approach a steady state of evaporation, but transient heating splits the phase conditions into distinct stages based on the time and energy absorbed in the initial heating window. These factors determine whether a droplet will undergo what Sigalotti called a “violent transition into a vapor” or whether it will slowly evaporate.

“This produces a memory effect where the stability and the size of the droplet are determined by its previous exposure to heat,” Sigalotti said.

Sigalotti said that their most surprising result was the sensitivity shifts between the nucleate-like and film-like boiling regimes. They observed that the size of the droplet was sensitive to heating time during the nucleate-like stage, but once it transitioned to the film-like stage, the droplet wasn’t as sensitive.

The researchers’ work established high-resolution benchmarks for transition thresholds and vapor evolution in droplets under microgravity. These benchmarks were validated by a 3D convergence study of droplets in resolutions of over 500,000 particles.

“It also offers a mathematical framework for predicting the final equimolar radius of a droplet based on its heating time,” Sigalotti said.

Source: “High-fidelity three-dimensional smoothed particle hydrodynamics simulations of evaporating liquid droplets in zero-gravity under transient and uniform heating,” by L. Di G. Sigalotti, L. Díaz-Damacillo, Luis A. Pascual, C. E. Alvarado-Rodríguez, and G. Odriozola, Physics of Fluids (2026). The article can be accessed at https://doi.org/10.1063/5.0318315 .